python中waitKey实例用法讲解

1、说明

用于等待按钮。当用户按下按钮时，句子将被执行并获得返回值。

2、语法

retval=cv2.waitKey([delay])

Retval：表示返回值；
Delay：键触发的时间，单位为ms。

3、实例

import cv2
lena=cv2.imread(\"D:\\pmjcv\\lena.bmp\")
cv2.namedWindow(\"lesson\")
cv2.imshow(\"lesson\",lena)
key=cv2.waitKey()

实例扩展:

# 需要导入模块: import cv2 [as 别名]
# 或者: from cv2 import waitKeyEx [as 别名]
def on_process_messages(self, sleep_time=0):

        has_windows = False
        has_capture_keys = False

        if len(self.named_windows) != 0:
            has_windows = True

        if len(self.capture_keys_windows) != 0:
            has_capture_keys = True

        if has_windows or has_capture_keys:
            wait_key_time = max(1, int(sleep_time*1000) )
            ord_key = cv2.waitKeyEx(wait_key_time)
            
            shift_pressed = False
            if ord_key != -1:
                chr_key = chr(ord_key) if ord_key <= 255 else chr(0)

                if chr_key >= \'A\' and chr_key <= \'Z\':
                    shift_pressed = True
                    ord_key += 32
                elif chr_key == \'?\':
                    shift_pressed = True
                    ord_key = ord(\'/\')
                elif chr_key == \'<\':
                    shift_pressed = True
                    ord_key = ord(\',\')
                elif chr_key == \'>\':
                    shift_pressed = True
                    ord_key = ord(\'.\')
        else:
            if sleep_time != 0:
                time.sleep(sleep_time)

        if has_capture_keys and ord_key != -1:
            self.add_key_event ( self.focus_wnd_name, ord_key, False, False, shift_pressed)